Method of producing petroleum



Dec. 11, 1945. P. D. BARTON ETAL. 2,390,770

METHOD lOF PRODUCING PETROLEUM I Filed Oct. l0, 1942 Patented Dec. ll, 1945 METHOD F PRODUCING PETROLEUM Paul D. Barton, Phoenixville, and Patrick F. Dougherty, Chester, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey lApplication October 10, 1942, Serial No. 461,536

1 Claim.

The present invention is directed to a method for the recovery of oil from wells in oil producing formations, and more particularly relates to the recovery of oil from wells from which production by conventional methods has decreased' tion or portions of the'oil which remains in the formations have found practical use, among them may be mentioned various gas re-pressuring, gas or Water drive, Water flooding methods and the like. However, such supplementary recovery methods by no means exhaust the oil producing formations of all the oil which they contain.

The present invention is directed to a method of increasing the recovery from virgin, depleted or partially depleted oil producing formations which will hereinafter be referred to as sands although it is to be understood that the inventionis applicable to other types of oil producing formations. It is also applicable to the exploitation of shale or asphaltic deposits.

Broadly stated, our invention comprises injecting air, or other combustion supporting gas, which will be referred to herein only as air,A into an oil producing formation through one well, hereinafter called an injection well, igniting a portion of the oil, or other hydrocarbons present in the pores of the formation at the face of the injection well, and continuing the supply of air to the formation through the injection well to support combustion of a portion of the hydrocarbons present in the formation. The hot products of combustion will spread through the formationdriving oil and gas present in the pores of the formation towards other wells in the same formation located at points adjoining or surrounding the injection well, and the oil and gas may then be recovered from such other wells,

which will be called herein production Wells.

We are aware that it has heretofore been proposed to ignite the oil in the oil bearing formation and to use the products of combustion tov in its more lspeciflc features, our invention relates to a method of controlling the rate and direction of combustion, both for the purpose of controlling the drive of the oil from the formation to producing wells and additionally for controlling the type of products produced.

For a better understanding of the invention,

reference should be made to the accompanying drawing, in which Fig. 1 is a diagrammatic sectional vieW of an oil field in which our invention is being practiced, while Fig. 2 is a plan view of such a field;

VIn the drawing A designates an oil producing formation, B designates an injection well, while C, D, E, F, G, and Hv represent producing wells surrounding Well B. Air from a compressor l flows through line Il to well B and is injected therethrough into the formation A. In 'starting up, injection of air is continued until tests show that the atmosphere in Well B is such that no explosion will occur on ignition. The oil or other hydrocarbons still remaining in the pores of the formation A at the face of the well B is then ignited by any suitable means, such as an electrical ignition device, themnite bomb or the like. The injection of air through well B is continued in order to support combustion of the hydrocarbons in the formation A. The hot products of combustion are driven through the formation A toward producing wells C to H and drive oil and gas remaining in the interstices of the formation Generally, at the start of operations, liquid production will be obtained, and due to the 10W pressure in formation A it is necessary to pump the producing wells C to H in the customary manner in order to remove the oil therefrom. However, after operations have continued for a considerable time, suicient pressure may be built up in the formation A to cause the producing wells to flow without pumping. Unless otherwise specified, the oil and gas produced from formation A' through producing wells C to H is removed therefrom through valved line 2, ows to manifold or collecting line' 3, a compressor 4 being provided` in such of lines 2 as may be necessary in order to raise the pressure therein sufficiently to cause the oil or gas flowing therethrough to enter collecting line 3 and thence to flow to oil and gas separator 5 wherein the oil is separated from the gas in well known manner. The oil is. removed 'from separator 5 through line 6 andis pumped to storage. Gas is removed from separator through line 1 and flows to compressor 8, where it is recompressed to the desired pressure and flows therefrom to manifold or distributing line '9. The gas may then be sold for fuel if it has sufficient caloric value and a market exists therefor, but as a general rule itis preferable to use the gas as an aid to further production in one of the manners hereinafter disclosed, since gas is generally at a premium in fields where the use of our process is economically justified. Distributing line 9 is therefor connected to each of producing wells C to H by a valved line I0.

The heat of combustion in the zone surrounding well B will heat the oil present in the formation and tend to crack heavier hydrocarbons present and vaporize any lighter hydrocarbons thus formed or naturally present in the formation. Such heating of the oil will, of course, reduce its viscosity and cause it to be more readily driven through the formation to the producing wells C to H. The lighter hydrocarbons formed by cracking will, of course, be vaporized by the high temperatures near the well B. but as they are -drlven through the formation will cool and condense and will therefore be absorbed by the oil present in the formation. reducing its viscosity and thereby aiding in production. 'I'he gaseous products of combustion, particularly the carbon dioxide, are readily soluble in the oil present in the formation and also aid in reducing its viscosity. If the formation A happens to be alimestone formation, the heat of combustion will tend to decompose it and produce further carbon dioxide, which will be absorbed by oil in the formation with consequent reduction in viscosity of the oilA and increase in its recovery. The injection of air through well B is continued at a rate such that combustion will be supported in the formation A and the zone of combustion will spread radially from well B through formation A.

As injection of air is continued through injection and combustion well B, it frequentlyoccurs that combustion will progress more rapidly toward certain of the production wells C, D, E, F, G, or H than itdoes towards other ofvthese wells. This condition will occur when the oil producing formation A is not of uniform permeability, as is frequently, if not generally, the case. For example` itmay frequently be the case that the formation A will be more permeable in the direction of well C than it is in the direction of well D. while the permeability of formation A is substantially uniform in the direction of wells E to H inclusive. When this condition is encountered, the air injected through injection yand combustion well B will flow in greater volume toward well C and in relatively small volume toward well D and in intermediate volumes toward wells E to H inclusive. Therefore, after combustion has continued for a time, the face of combustion in formation A may assume a plan view similar to that shown by dotted line X in Fig. 2. in which it will be noted that combustion has proceeded much further toward well C than it has toward well D but is proceeding in a satisfactory manner toward wells E to H inclusive.

Such unevenness vin the rate of combustion from the injection well to the various produc.- tion wells can generally be detected without difficulty; Thus a greater quantity of oil is generally produced from the well or wells toward which combustion is proceeding most rapidly,

well C in the example being given; also the type of products produced from the well toward which combustion is proceeding most rapidly will differ from the products produced at the wells toward which combustion is proceeding at a slower rate, lighter hydrocarbons and a largequantity of gas and possibly some products of combustion being produced at those wells towards which combustion is proceeding most rapidly. In addition, the temperature 'of the fluids. particularly the gas andsproducts oi' combustion obtained from the well or wells toward which combustion is proceedingr most rapidly, will be higher than it is at other wells.

For the more nearly perfect recovery 'of oil from the formation A, it is desirable that the .combustion progress uniformly radially from well B toward all of the producing wells, and therefore it is necessary to so control the combustion as to keep the rate of combustion substantially uniform. Thus, if channels should be encountered or develop in formation A in the direction of well C with the result that the combustion tends to proceed toward this well more rapidly than toward well D, while combustion towards weils E to H inclusive is proceeding in a satisfactory manner, steps must be taken to decrease the rate-of combustion toward well C or increase it toward well D, or a combination of these steps must be taken. In order to decrease the rate of combustion toward well C, Well C may be shut down by throttling, to the extent if necessary of closing, the line 2 conm neeted thereto. until such time as combustion toward well D has caught up with thev combustion toward weil C. Such a remedy may be suf,- licient if there is only a relatively slight difference in the rate of combustion toward well C and D; but, if that remedy is inadequate, additional pressure may be built up in well C by opening valved line I0, whereby all or part of the gases produced through wells D to H inclusive from formation A are injected back into well C. thereby causing the air injected through well B to pass more readily toward well D.

Another method of decreasing the rate of combustion toward weil C is to inject water through well B. The water, in following the same channels that the gas follows, will pass linto the more permeable formations in greater amount than into the less permeable formations and thus,

when air is again injected, will decrease the rate of combustion toward well C by obstructing the air ow in this direction proportionately greater than in other directions as well as by exerting a greater quenching action on the combustion in this direction. In order to effect a more per-- channels are located near 'the face of well B.v

However, in case the channels occur further back in formation A, it is preferable to inject with the water some substance in solution theredwith but which will be precipitated therefrom by chemical action with the formation after it has penetrated back into formation A. Such action will materially throttle the channels in the direction of the well C and aid in maintaining around well D opened up.- Also, acid may be introduced .through well B after introducing therethrough some material to close up the pores toward well C so that the acid will tend to go Ainto the direction of well D and open up the pores in formation A toward this well.

Having now described our invention, what we claim and desire to protect by Letters Patent is:

In the recovery of petroleum from a number of wells penetrating a single underground formation from which petroleum production has materially decreased, and wherein a combustionsupporting gas under pressure is introduced to said formation at one locus and the petroleum ignited and combustion supported by continuing the supply of said combustion-supporting gas,

Ain

thereby causing said zone of combustion to advance and drive petroleum throughv said formation from said locus toward said wells and withdrawing petroleum from said wells, the improvement which comprises more nearly equalizing the progress of combustion toward the several wells, where the zones of the formation leading thereto are of substantially different permeability, by examining and determining the quantity and character of petroleum products withdrawn from the several wells and thereby determining variations in the rates of combustion through said formation to 'the several wells, and then establishing substantial uniformity in said rates of combustion by decreasing the resistance to advancement of combustion through one or more said zones in which the combustion is proceed.- ing at too slow a rate by introducing into a well communicating with a zone an acidic material for the purpose of penetrating the formation in said zone and therebyopening its pores progressively in a direction opposite to thatV of the direction of advancement of combustion to thus provide a free passageway for the petroleum products. l

PAUL D. BARTON.

PATRICK F. DOUGHERTY. 

